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Arctic sea ice loss responsible for Eurasia's deep chill

A deadly winter cold wave settled over Europe at the end of January 2012, blanketing much of the continent with snow and ultimately causing more than 800 deaths. Such severe winters are becoming more common across Eurasia—and some scientists contend that sea ice loss, by altering circulation patterns, is ultimately to blame for these frequent deep chills. But as climate simulations haven’t yet parsed out the atmospheric response to the loss of sea ice, its influence on Eurasian winters remains a question mark. Now, a new modeling study finds a link between these winters and the decline of sea ice in a part of the Arctic Ocean known as the Barents-Kara sea region, bordering Norway and Russia. The researchers identified several key circulation patterns that affected the winter temperatures from 1979 to 2013, particularly the Arctic Oscillation (a climate pattern that circulates around the Arctic Ocean and tends to confine colder air to the polar latitudes) and a second pattern they call Warm Arctic and Cold Eurasia (WACE), which they found correlates to sea ice loss as well as to particularly strong winters. WACE has been going strong since about 2004 or 2005—and as a result, the probability of severe winters has more than doubled in central Eurasia, they report online today in Nature Geoscience. But these severe winters may be a temporary phase within longer term warming: By the end of the century, the researchers report, the Arctic Oscillation could overpower the cooling effect from WACE—and winter temperatures over Eurasia will gradually increase.